The field of the invention relates to control of fuel delivery to an internal combustion engine via a returnless fuel system.
Conventional fuel systems deliver fuel to a fuel rail having fuel injectors connected thereto via an electric pump. Fuel pressure is maintained at the fuel rail by a pressure relief valve and return line back to the fuel tank.
Returnless fuel systems are also known in which the pressure relief valve and return fuel line are eliminated. Pressure at the fuel rail is maintained at a desired level by varying the voltage supplied to the fuel pump. Either the voltage amplitude is changed or a constant voltage amplitude is used and electrical power varied by pulse width modulating the voltage signal. An example of such system is shown in U.S. Pat. No. 5,355,859 in which fuel pressure is regulated as a function of engine load.
The inventors have recognized numerous problems with the above approaches. For example, more fuel pressure is applied than is needed over many engine operating conditions. Accordingly, electrical power is wasted resulting in a loss of fuel economy.